JACK COLBACK'S decision to walk away from Sunderland as a free agent to join arch-rivals
Sunderland had fresh talks in February with the 24-year-old about a new contract, which had been in danger of expiring after a failure to agree terms earlier, but talks are understood to have been put on hold until Premier League status had been assured.
But in early May suggestions started to surface that Colback had attracted interest from Newcastle, Hull City and numerous other top-flight teams.
At that point Sunderland claim to have been knocked back in attempts to get the player to return to the negotiating table and commit his future to the club where he had progressed through the academy.
Long-serving Colback's decision has clearly rattled Sunderland and, shortly after news broke of his move last night, Sunderland issued a statement condemning his actions.
There were also Tweets from Sunderland's official Twitter account with photos displaying his celebrations after February's 3-0 win at St James' Park in the Tyne-Wear derby, when Colback actually scored.
The statement read: "Jack is a player we have nurtured and developed through our academy system since he was eight-years-old. We gave him the opportunity to become a professional footballer and are therefore extremely disappointed in the events that led to his departure from the club.
"This wasn't about money; the club agreed to all of the terms demanded of us during discussions and we were always led to believe that Jack wanted to stay with us.
"At his and his representatives request, final talks were put on hold until the club secured its top-flight status. To our dismay, however, we were subsequently never given the chance to negotiate with him to stay.
"For him to then leave the club that has supported him throughout his formative years in such a manner, with no chance for Sunderland to recover any of the significant investment that it has made him as a player, has left a bitter taste."
Colback, brought up in Killingworth, has signed a long-term deal at Newcastle and has been quick to reveal his delight for joining the club he supported as a boy.
He made 137 appearances after breaking in to the first team picture at Sunderland in 2008. Poyet had earmarked Colback as one of the players he wanted to stay ahead of a summer when significant changes are planned.
After convincing Swedish midfielder Seb Larsson to stay for a further three years, Colback was seen as another player Poyet would have preferred to keep after keeping the Black Cats in the top tier of the English game.
Colback is thought to have rejected an initial offer from Sunderland last summer. In failing to reach an agreement before the contract entered its final year, however, there was always a danger he would move on for nothing.